In my experience, hitting into a net is great practice IF you record a lot of video and check your alignments as you go. Without that video check up there is definitely a risk of ingraining a bad swing. For me, and my particular issues, a DTL view to check my swing path is essential.
Hitting into a Net - Page 14
I'll practice on my net and periodically hit the range to check on my ballflight.
Turned out to be the best thing for me since it just seemed so much easier for me to focus on my swing and the technique these specific drills were intended to improve. The key (for me at least) was sticking to what my instructor wanted me to practice which was all about ingraining new and better swing fundamentals regardless of ball flight (at least at this point of my "re-training").
I happened to be watching the Golf Channel last night (and not just so I could see Holly) and I think it was Martin Hall who said something like "Exagerate, Exagerate, and then Integrate" when it came to incorporating new swing techniques. I think hitting into a net lets you exagerate those new motions best since you don't get caught up in where the shot is going. I certainly think you also need to see how that eventually translates into a full swing out on an open range so this year I'll be combining both "net" swings and "outdoor" swings into my practice routines, especially for those first few practices after each lesson.
Unfortunately, it seems like fates against me since it's been super cold for the most part and it seems like it's snowing every week.
I can't practice with my net indoors and have only been able to use it a handful of times in the 8 weeks I've had it.
I'm about to enter one of the two busiest months of my work year so I'll have a very little time to use the mat and net.